The radionuclides Ga67, In111, and Bi206 have been found to have an affinity for soft tissue tumor in both animals and man. The aim of this project is to determine the mechanism(s) and biochemical agent(s) involved in the deposition of these materials in both normal and malignant tissues. We plan to test various means for separating in a high state of purity the small subcellular granules (as opposed to normal lysosomes) that hve been shown to be responsible for most of the particulate binding of Ga67 and 111In in tumor cells (as opposed to normal cells) so that the exact nature of these particles may be determined. A more precise separation of those organelles that bind Bi206 will also be attempted. Chromatographic and electrophoretic techniques along with various automated bioanalytical techniques will be used to determine the nature of the 5-4 x 10 to the 4th power MW macromolecular component(s) that account for a high proportion of the binding of Ga67 and 111In in extracts of tumor and thymus tissue (as contrasted with tat seen in other normal tissues). Tissue culture studies will also be initiated to determine in different cell lines what factors in the culture media lead to Ga67 uptake an whether the uptake observed is reversible or not. preliminary tissue culture studies with 111In and Bi206 may also be initiated.